Yes, the rest of the Cavs did not play well. But that was the best (statistically) that Lebron has ever played in a Finals Game. I doubt he continues at that level. And Curry and Thompson played a bit below their level too.
All that when really my biggest take away from game 1 is this: If Lebron makes that last shot OR the put back goes in, everyone is freaking out and saying since Cleveland stole on in GS they are now the favorites (especially since that means Irving never gets hurt). Instead GS pulls away in OT, and now everyone is saying GS could possibly sweep. This is a 6+ game series. And it will be a fun one.